The compound 9,10-bis(chloromethyl)anthracene
is a compound of high interest as an intermediate for chemical synthesis processes where the inclusion of an anthracene skeleton that is doubly substituted in the meso or benzylic position (CH2 adjacent to the aromatic ring) is necessary.
Document J. Am. Chem. Soc. 1955, 77, 2845-2848 describes a chloromethylation method of anthracene as a versatile intermediate in obtaining other derivatives by means of displacement reactions, that is, from 9,10-bis(chloromethyl)anthracene to a wide range of available functionalisation. In summary, the synthetic method described in this document consists of passing a current of cool hydrogen chloride, continuously generated in situ, to a mixture of 1,4-dioxane, anthracene, p-formaldehyde and fuming hydrochloric acid. The crude reaction product is heated under reflux, maintaining the current of hydrogen chloride for several hours, after the interruption thereof, the reflux system continues for another 24 hours. After filtering and thorough washing to remove impurities, the compound is finally obtained in solid form with a fairly moderate yield of 67%. As can be seen, it is a rather laborious experiment with a yield that can be significantly improved.
Other synthetic methods have been described in the state of the art, such as that described in RSC Adv. 2015, 5, 73951-73957, where the synthesis is carried out in the presence of an organic solvent (dioxane) and at high temperatures (100° C.).
However, the inventors of the present application have found serious reproducibility problems in this method. When the inventors reproduced the method, they found that 9,10-bis(chloromethyl)anthracene is not obtained, as stated in the scientific article, despite having repeated this reaction several times, and being unsuccessful every time. Therefore, this synthesis route must be discarded.
9,10-bis(chloromethyl)anthracene can be acquired from different suppliers. On their website, Sigma-Aldrich classifies this product within a selection of “uncommon and unique chemical reagents”, thus justifying its fairly high price. However, this compound is widely used in scientific work as a structural intermediate for anthracene, which is freely chemically derivatised, mainly seeking the occurrence of colorimetric and fluorescent optical properties.
Some applications of this compound have been published in the state of the art.
Document RSC Adv. 2015, 5, 73951-73957 describes this compound as a new photoactive cyclophanes skeleton with molecular rigidity for use in specific recognition, electronic molecular machines, drug carriers and catalysts in organic synthesis.
Document Chem. Mater. 2004, 16, 2783-2789 describes this compound as organic matter for application in optical fluorescence, photodynamic therapy and optical data storage and microfabrication through donor-bridge-acceptor compounds or donor-bridge-donor compounds.
This compound acts as a valuable precursor in the preparation of anthracene meso bi-substituted derivatives in positions 9 and 10, such as amines and the respective hydrochlorides thereof, amides, isocyanates, alcohols, esters, ethers, thiols, nitriles, acids and phosphonates.